Fundamental studies of the crucial, inevitable interactions of cations with ribosomes will be undertaken. The interrelated and sometimes antagonistic effects of M ion and M2 ion on cation binding, on electrostatic free energies, and on local potentials of ribosomes and ribosomal subunits will be established, and evaluated in the light of modern electrostatic theories of macromolecules. The necessary data will be obtained by combining standard ion-binding techniques, electrophoretic studies, and reporter-group determinations of local potentials. The effect of pressure on ribosome-subunit association will be studied from this point of view, to test a hypothesis that large-scale displacement of M2 ion and its associated electrostatic consequences are primarily responsible. Pressure-jump kinetic studies of ribosome dissociation (as a function of (M ion), (M2 ion), and for jumps of as much as 1500atm) will be used to validate or refute my previously published view of the rate-controlling processes of subunit dissociation. The combined accessible range of pressure and (M2 ion) variation will change the free energy of ribosome dissociation (i.e., the net of all intersubunit interactions) by between 9 and 18 kcal, depending on the degree to which the effects are independent. This range is more than adequate to reverse any of the reactions of the initiation of protein synthesis at will. Using fluorescent derivatives of N-acyl meth ionyl tRNA and possibly of initiation factors, we will be able to determine IN SITU, without recourse to filter-binding or sucrose-gradient techniques, whether binding of initiator tRNA to 70S particles is limited by ribosome dissociation (obligatory 30S initiation) or not (direct 70S participation).